Disk drives are information storage devices that use magnetic media to store data and a movable read/write head positioned over the magnetic media to selectively read data from and write data to the magnetic media.
Consumers are constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations. Thus, disk drive manufacturers have continued to develop higher capacity disk drives by, for example, increasing the recording and reproducing density of the information tracks on the disks by using a narrower track width and/or a narrower track pitch. However, each increase in track density requires that the disk drive device have a corresponding increase in the positional control of the read/write head in order to enable quick and accurate reading and writing operations using the higher density disks. As track density increases, it becomes more and more difficult to quickly and accurately position the read/write head over the desired information tracks on the disk. Thus, disk drive manufacturers are constantly seeking ways to improve the positional control of the read/write head in order to take advantage of the continual increases in track density. One common approach is to employ a dual-stage actuator system.
FIGS. 1-2 show a conventional disk drive unit having dual-stage actuator system. Such dual-stage actuator system includes a primary actuator such as a voice-coil motor (VCM) 107 and a secondary micro-actuator such as a PZT micro-actuator 105. A disk 101 of the disk drive unit is mounted on a spindle motor 102 for spinning the disk 101. A voice coil motor arm 104 carries a head gimbal assembly (HGA) 100 that includes a slider 103, the PZT micro-actuator 105 and a suspension 106 to support the slider 103 and the PZT micro-actuator 105. A read/write head is embedded in the slider 103.
The voice-coil motor 107 as the primary actuator controls the motion of the voice coil motor arm 104 and, in turn, controls the slider 103 to position with reference to data tracks across the surface of the disk 101, thereby enabling the read/write head to read data from or write data to the disk 101. As compared to the voice-coil motor 107, the PZT micro-actuator 105 corrects the displacement of the slider 103 on a much smaller scale in order to compensate for the resonance tolerance of the VCM and/or the HAA (head arm assembly). Therefore, the PZT micro-actuator 105 enables, for example, the use of a smaller recording track pitch, and thus increases the “tracks-per-inch” (TPI) value for the disk drive unit, as well as provides an advantageous reduction in the head seeking and settling time. Thus, the PZT micro-actuator 105 enables the disk drive unit to have a significant increase in the surface recording density of the information storage disks used therein.
FIGS. 3-4 illustrate the HGA 100 with dual-stage actuator system in the conventional disk drive unit shown in FIGS. 1-2. The suspension 106 of the HGA 100 comprises a flexure 122 having a plurality of traces, a slider support 121, a metal base 123 and a suspension load beam 124 having a dimple 125 to support the slider support 121 and the metal base 123. The flexure 122 connects the slider support 121 with the metal base 123 via the traces. The flexure 122 has a PZT mounting region 128 for mounting the PZT micro-actuator 105 and a slider mounting region 129 at a tongue region thereof. The slider 103 is partially mounted on the slider support 121 via the slider mounting region 129. The slider support 121 forms a bump 127 thereon to support the center of the back surface of the slider 103. The dimple 125 of the suspension load beam 124 supports the bump 127 of the slider support 121, which enables that the load force from the load beam 114 evenly applies to the center of the slider 103 when the slider 103 flies over the disk 101. The PZT micro-actuator 105 comprises two thin film PZT elements 10 which are connected with each other. The two thin film PZT elements 10 are mounted on the PZT mounting region 128 of the flexure 122.
As shown in FIG. 5, when a voltage is input to the two thin film PZT elements 10, one of the PZT elements may contract while the other may expand, thus making the slider support 121 and the slider 103 rotate against the dimple 125 of the suspension load beam 124, thereby achieving a smaller adjustment for the displacement of the slider 103. The deformation function of the PZT elements 10 is determined by the structure of the PZT elements themselves. Referring to FIG. 5a, a typical PZT element has multiple PZT layers such as PZT layers 702, 703 laminating together to form a layered structure and each PZT layer is sandwiched between a pair of positive-negative electrode layers 704/705, 706/707. The positive layers 704, 707 of the PZT layers 702, 703 connect with each other by sputtering process at the inner of the layered structure to form a positive electrode of each PZT element. Similarly, the negative layers 705, 706 of the PZT layers 702, 703 also connect with each other by sputtering process at the inner of the layered structure to form a negative electrode of each PZT element. The positive electrode and negative electrode of each PZT element 10 respectively forms an electrical pad 131, 132. Shown in FIG. 4, after the electrical pads 131, 132 of the PZT elements 10 are respectively and electrically connected (usually gold trace bonding) with the electrical pads 133, 134 formed on the flexure 122, the PZT elements could be driven to operate by applying voltage to electrical pads 133, 134.
In addition, as shown in FIGS. 3, 4 and 5a, the present PZT actuator 105 is primarily formed by two symmetrical PZT elements 10 connected with each other. The two identical PZT elements 10 are mechanically connected by a thin material thus to be mutually combined. For example, the PZT elements 10 connect with each other by a substrate layer 701.
Though the above-mentioned PZT micro-actuator 105 could provide smaller scale adjustment for the displacement of the slider, the PZT micro-actuator 105 has some insuperable drawbacks. First, because the present PZT micro-actuator 105 for HAG is formed by two piece PZT elements mechanically connecting with each other via thin material and the mechanical connection in usual cases possesses an extremely low strength at the connection point, the connection point is easy to deform or break in the technological operation or transformation or testing process of the PZT micro-actuator 105, thereby causing the whole PZT micro-actuator 105 damaged. Second, the two piece PZT elements which are integratedly connected with each other easily causes an increase of the manufacture cost. For example, on the one hand, when it is detected that one PZT element is damaged and thus should be discarded while the other PZT element is in a sound condition, the sound PZT element has no choice but to be also discarded as the two piece PZT elements are combined together, thereby causing the increase of the manufacture cost. on the other hand, as mentioned above, the corresponding electrode layers of all the PZT layers in the present PZT element are connected correspondingly (for example, all the positive electrodes are connected together and all the negative electrodes are also connected together). That is, all PZT layers are parallelly connected between one pair of electrode layers, thus it is unable to detect the defect of a single PZT layer. In other words, when one PZT element is damaged, it is impossible to detect which PZT layer of the PZT element is damaged, thereby the whole PZT element has to be discarded. Similarly, as the corresponding electrode layers of all PZT layers are connected correspondingly by sputtering as mentioned above, the manufacture process is complex, further causing a higher manufacture cost.
Another drawback existing in the conventional HGA 100 shown in FIGS. 3, 4 relates to electrical connection method and shock performances. As mentioned above, after the PZT elements 10 are bonded to the HGA 100, the electrical pads 131, 132 of the PZT elements 10 are respectively connected with electrical pads 133, 134 formed on the flexure 122 via gold trace soldering. As the whole structure of gold trace soldering possesses an extremely poor shock performance, it is easy to split or break especially when outer vibration or shock event happens. Hence the whole structure of the HGA 100 has a terribly poor shock performance.
Besides, the prior art has other drawbacks. As the slider support 121 is coupled with the metal base 123 by the traces of the flexure 122 which are only 10-20 um in thickness and formed from soft polymer material, the flexure 122 is easy to distort and accordingly the suspension 106 is likely to deform during the suspension manufacture process, HGA manufacturing and handle process. Moreover, the suspension deformation resulted from such weak structure will adversely cause the suspension or HGA dimple separation. FIGS. 6 and 7 respectively show a suspension deformation and a dimple separation. In addition, as the slider 103 is partially mounted on the slider support 121 and the slider support 121 is coupled with the metal base 123 via traces of the flexure 122, the static attitude of the slider 103 such as PSA (pitch static attitude) or RSA (roll static attitude) is unstable and difficult to control, which causes the HGA performance unstable and accordingly, affects the HGA dynamic performance seriously, especially when a vibration or shock event happens or during the manufacture process or handle process. Finally, such structure makes the whole HGA a poor shock performance. When a vibration or shock event happens, for example tilt drop shock or operation shock, the suspension or the PZT elements of the PZT micro-actuator 105 may be caused to damage.
Hence, it is desired to provide an improved structure to solve the above-mentioned problems.